hg: jdk9/hs-rt/hotspot: 8087143: Reduce Symbol::_identity_hash to 2 bytes

[yumin.qi at oracle.com]

Changeset: e532b042ad77
Author:    minqi
Date:      2015-06-29 13:48 -0700
URL:       http://hg.openjdk.java.net/jdk9/hs-rt/hotspot/rev/e532b042ad77

8087143: Reduce Symbol::_identity_hash to 2 bytes
Summary: Convert Symbol::_identity_hash from integer to short integer to save two bytes. Also change identity_hash() to have 'this' and first two bytes of symbol join the calculation.
Reviewed-by: iklam, coleenp, shade

! agent/src/share/classes/sun/jvm/hotspot/oops/Symbol.java
! src/share/vm/oops/symbol.cpp
! src/share/vm/oops/symbol.hpp
! src/share/vm/runtime/vmStructs.cpp